1. Field
This invention relates to the removal of residue, such as varnish, from fuel storage tanks and, in particular, from aircraft storage tanks which often include areas which cannot be reached by a direct spray from a nozzle located near the tank access port.
2. Prior Art
One common method used to clean an aircraft wing tank is to loosen the residue with a solvent and then scrub the tank by hand with a brush. In carrying out this method, the operator is often required to place his head in or near the tank access port to view his progress and to reach points at some distance from the access port. The strong fumes from the solvent tend to make the operator unconscious, making this work dangerous, tedious and costly. In addition, the working space surrounding the access port, such as an aircraft hangar area, fills with these fumes.
Attempts have been made to overcome these problems. In particular, K. R. Witcomb in U.S. Pat. No. 2,733,723, shows a bar type spray nozzle extending through several wing ribs with multiple ports to spray solvent in a number of diverse directions. A single collection port is used to drain the solvent. Unfortunately, the wing ribs in a number of modern aircraft do not have clear areas which would enable a pipe nozzle to be passed through several ribs in a straight line, nor is the access port always sufficiently wide to permit such a nozzle to be placed within the wings. For the wings to accommodate a long nozzle, it must be constructed of sections that can fit through the access port for reassembly within the wings . The reassembly is usually inconvenient and, in some cases, awkward or impossible. In addition, some aircraft have areas which are inaccessible to the spray emanating directly from such a nozzle, resulting in an incomplete cleaning that must be corrected by resorting to manual methods which defeats the purpose of the system.
This prior art system drains the solvent from a low point on the wing. This causes solvent and residue to become trapped along the wing structure before reaching the drain port. No solvent is drained from the access port through which the nozzle is placed. Usually the nozzle feed line is smaller than the access port and to prevent solvent from leaking about this port requires a special fitting.